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https://issues.apache.org/jira/browse/PDFBOX-4889?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17138541#comment-17138541
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Michael Klink commented on PDFBOX-4889:
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The *AcroForm* form structure of the PDF is utterly broken. But that's not the
problem here.
The problem is that some of the widget annotations referenced from the document
page have a non-empty *Rect* but a normal appearance with an empty (0×0)
*BBox*. When displaying or flattening that widget, the *BBox* area of that
appearance must be moved and scaled to fill the widget *Rect*. But that is
impossible, you cannot scale a zero width or height by a finite real number to
fill a none-zero width or height. Unfortunately PDFBox does not check for this
situation and tries to scale by infinity. This in turn eventually is caught by
some later concatenation of the scaling with another transformation, resulting
in the observed exception.
As an example the field with the partial name
"topmostSubform[0].Page1[0].f1_1[0]" (which is an invalid _partial_ name) has a
*Rect* {{[ 36 684 467.25 698.001 ]}} and its normal appearance has a *BBox*
{{[0 0 0 0]}}.
Strictly speaking this PDF is broken. But a more benign behavior of PDFBox
would be to recognize the broken appearance and ignore it.
I'm not sure whether a new annotation should be built and flattened instead or
whether the field should be completely ignored. In the case at hand the result
would be identical because (at first glance) the fields with these invalid
empty normal appearances also have no value.
> Cannot flatten this file.
> -------------------------
>
> Key: PDFBOX-4889
> URL: https://issues.apache.org/jira/browse/PDFBOX-4889
> Project: PDFBox
> Issue Type: Bug
> Components: AcroForm
> Affects Versions: 2.0.20
> Reporter: Jief Knudsen
> Priority: Major
> Attachments: f1040sb test.pdf
>
>
> Calling pdfDoc.getDocumentCatalog().getAcroForm().flatten() gives
> "Multiplying two matrices produces illegal values"
>
>
>
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